1. Field of the Invention
The present invention concerns an oscillating arm suspension unit for vehicles.
To be more precise, it concerns a suspension unit of the type comprising:
a support adapted to be fastened to a framework of the vehicle, PA1 a longitudinal arm, PA1 means coupling a rolling member to the arm defining a transverse first axis about which the rolling member rotates relative to the arm, PA1 means coupling the arm to the support defining a transverse second axis about which the arm rotates relative to the support, the second axis being parallel to the first axis and offset relative to it in a longitudinal direction, PA1 a longitudinal cylinder within the arm, PA1 a piston slidable longitudinally within the cylinder and delimiting with it a fluid-tight enclosure, PA1 a compressible fluid in the enclosure serving as spring means, PA1 a rod linking the piston and the support, PA1 means pivoting the rod to the support for rotation about a transverse third axis parallel to the second axis and offset relative to it transversely, and PA1 means pivoting the rod to the piston for rotation about a transverse fourth axis parallel to the third axis. PA1 a support adapted to be fastened to a framework of the vehicle, PA1 a longitudinal arm, PA1 means coupling a rolling member to the arm defining a transverse first axis about which the rolling member rotates relative to the arm, PA1 means coupling the arm to the support defining a transverse second axis about which the arm rotates relative to the support, the second axis being parallel to the first axis and offset relative to it in a longitudinal direction, PA1 a longitudinal cylinder within the arm, PA1 a piston slidable longitudinally within the cylinder and delimiting with it a fluid-tight enclosure, PA1 a compressible fluid in the enclosure serving as spring means, PA1 a rod linking the piston and the support, PA1 means pivoting the rod to the support for rotation about a transverse third axis parallel to the second axis and offset relative to it transversely, and PA1 means pivoting the rod to the piston for rotation about a transverse fourth axis parallel to the third axis and comprising:
2. Description of the Prior Art
In known suspension units of this type, the means coupling the rod to the piston comprise a direct articulation of the rod to the piston about the fourth axis.
Movements of the suspension, that is to say rotation of the arm about the second axis relative to the support, necessarily result in an oblique disposition of the rod relative to the longitudinal direction of the cylinder, in certain angular positions of the arm relative to the support, and this oblique disposition results in the application to the piston by the rod of forces that are themselves oblique relative to the longitudinal direction of the cylinder; the longitudinal component of these forces results in longitudinal displacement of the piston relative to the cylinder in the manner required, but the transverse component of these forces results in increased friction between the piston and the cylinder, impeding longitudinal movement of the piston; also, given that the transverse forces to which the piston is subjected are transmitted to the cylinder through the seals, pivoting movement of the rod relative to the piston around the fourth axis results in varying compression of the seals between the piston and the cylinder which may lead to premature deterioration of the seals and the appearance of leaks between the piston and the cylinder.
These disadvantages are all the more significant in that the suspension arm tends to flex between its axis of rotation relative to the support and the axis of rotation of the rolling member relative to the arm, which results in deformation of the cylinder essentially in a plane perpendicular to the various axes of rotation, which is precisely the plane in which are developed the transverse components of force when the rod is offset angularly relative to the longitudinal direction of the cylinder; deformation of the arm then results in the appearance of additional transverse components of force between the piston and the cylinder and an increased risk of deterioration of the seals and appearance of leaks.
An object of the present invention is to alleviate these disadvantages.